Lennox · Furnace

E152 Refrigerant leak sensor #2 fault

High severity Lennox ML180UHE

What the control is telling you

The second A2L (low GWP) refrigerant detection sensor reports an internal problem and may need replacing. Clears when the sensor stops reporting the fault.

Applies to: ML180UHEK (R-454B era) single-stage 80% furnaces with integrated control 107792-XX (ML180UH045/070/090/110/135, incl. low-NOx X models)

Likely causes

Failed refrigerant detection sensor #2
Sensor contaminated or damaged

Test and repair steps

Confirm a second sensor is actually installed and the LGWP2 DIP switch matches (Enable only with two sensors).
Inspect sensor #2 and its plug for damage, dust, debris or moisture.
Reseat the sensor connector at the LGWP2 plug until the Molex clip locks.
If the fault stays, replace the sensor with a Lennox approved part.
Press the LGWP test button (short press) to re-evaluate the fault after repair.

Settings for these units

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Source: Lennox ML180UHEK Unit Information 100161/100166, Table 6 Integrated Diagnostic Codes, p.14; VII Low GWP Application, p.33-35. Summarized in our own words; check the original manual for your model.

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For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.